What I'd like to know is, would it be possible to display the output of an external opengl application inside Blender?
As shown on the image the left part is the standard 3D viewport, and on the right would be the output of an external renderer or game engine that would be displayed inside Blender directly.
A use case for this would be to use Blender as a level editor and seeing the edits being replicated live in the game engine.